Incredible Render Performance In Kdenlive With NVENC - But 1 Big Problem

[jb at kdenlive.org]

On July 16, 2018 3:48:21 PM GMT+02:00, Eugen Mohr <eugen.mohr at gmx.net> wrote:
>On a first look:
>
>File which runs:
>
>MLT version 6.7.0
>
>frame_rate_den="1"
>
>60 fps
>
>name="length">53282
>
> 
>
>file which doesn't run:
>
>MLT version 6.10.0 → version of the Kdenlive refactoring
>
>frame_rate_den="1001"
>
>29.97 fps
>
>name="length">00:14:48;00
>
> 
>
>check this parameters with other files
>

Thanks for this feedback. This could be very interesting and definitely deserves some investigation.

As Eugen stated, the main difference seems to be in the project profile. The first 'working' project uses a 60fps profile, while the broken one uses a 29.97 fps profile. And your source video (sintel) is a 24fps video. These parameters might affect nvenc. 

I would recommand testing directly with Mlt in a terminal:

melt -profile atsc_1080p_60 sintel.mp4 out=3600 -consumer avformat:result-60.mp4 f=mp4 vcodec=nvenc_h264 global_quality=21 vq=21 preset=slow bf=2

This should render the first minute with a 60fps profile

Then:

melt -profile atsc_1080p_2997 sintel.mp4 out=1800 -consumer avformat:result-2997.mp4 f=mp4 vcodec=nvenc_h264 global_quality=21 vq=21 preset=slow bf=2

This should render the first minute at 29.97 fps.

(Just adjust the path to the sintel.mp4 original video in my command lines).

What are the render times? Keep in mind that rendering at 60fps means you render twice as many frames compared to 29.97fps...

Some comparison between nvenc and the normal h264 encoder would be nice. Also interesting to see if the time gain is still there when you add effects, for example add:

-attach sepia
Just before the '-consumer' paramt to add a sepia effect to the clip

Best regards
Jean-Baptiste


>
>Gesendet: Montag, 16. Juli 2018 um 07:51 Uhr
>Von: johnar1 <johnar1 at protonmail.com>
>An: "kdenlive at kde.org" <kdenlive at kde.org>
>Betreff: Incredible Render Performance In Kdenlive With NVENC - But 1
>Big Problem
>
> 
>
> 
>
>System: i5 6600K, 1050TI, Ubuntu 18.04, Kernel 4.16
>
>I have successfully compiled mlt and ffmpeg with nvenc support using
>the official nvenc headers stripped from the Nvidia SDK.
>
>Rendering the first minute of the 1080p Sintel version, with 4 threads
>specified and my nvenc profile, finishes in 10 seconds.
>
>Sintel can be downloaded here: https://durian.blender.org/download/
>
>Nvenc Profile: (compatible with recent mlt versions who are nvenc
>enabled by deafult)
>
>f=mp4 vcodec=nvenc_h264 global_quality=21 vq=21 preset=slow bf=2
>ab=384k
>
> 
>
> 
>
>Now here is the problem that I do not understand:
>
>Using the latest version of kdenlive from the kdenlive-master ppa
>combined with the newly compiled versions of ffmpeg and mlt works
>perfectly, but only under very specific circumstances.
>
> 
>
>I have only been able to get rendering with nvenc to work properly when
>I use and open this specific kdenlive [b]save file[/b] which I made of
>the first minute of the Sintel short film with the Appimage Version of
>Kdenlive. After launching the ppa/installed version of kdenlive and
>opening this save file, rendering with nvenc works flawlessly.
>
> 
>
>If I simply start a new project, adding the whole Sintel short film to
>the project bin, cutting the first minute and render it, nvenc simply
>does not work and the render time is tripled, despite having changed
>nothing else, including the nvenc render profile.
>
> 
>
>If I create a save file of the first minute of Sintel with the
>installed version and open it on the Appimage version, nvenc does not
>work again.
>
> 
>
>Conclusion: There must be something in this save file, maybe a
>parameter, additonal settings or any type of code not present in the
>default kdenlive project profiles, which enables NVENC.
>
> 
>
>I would greatly appreciate it if we could find out the source of this
>problem together.
>
> 
>
>Kdenlive Appimage Save File with which NVENC works:
>
>https://pastebin.com/rzjR57DJ
>
> 
>
>PPA/Installed Version of Kdenlive created Save File which breaks NVENC:
>
>https://pastebin.com/3uQ8sP0C
>
> 

-- 
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